A typical projector apparatus of this type is a liquid crystal (LC) projector having the following configuration. White light emitted from a light source is split into three beams of primary colors, blue (B), green (G), and red (R), which are used to illuminate three liquid crystal panels (LCPs). The light beams emerging from the respective LCPs are synthesized by a color synthesizing prism of an image synthesizing device to form a trichromatic imaging light, which is projected by projection mirrors onto a front screen.
Since low-cost competition is very severe in the market of compact projector apparatuses, cost reduction effort for peripheral parts of an image synthesizing device is important. That is also the case with a prism alone.
For example, although aluminum die-casting of a prism fixing member is customary, use of a resin material has emerged in recent years to reduce the cost of the prism fixing member. However, in order to ensure the same reliability of such plastic fixation member as that of conventional one, an appropriate fixation method must be invented.